I've never really used TFS Source control offline before and have been in more projects where I have used the latest version of Visual Source Safe. In comparison TFS source control seems a lot more rich in features, sadly its missing one key feature that Source Safe was very good at and that's the ability to easily work offline and then check what ever changes you had back in and merge them with source safe.
I've found an interesting webcast on how to work offline with TFS using TFS Power Toy.